import java.util.List;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 晓星航
 * Date: 2022-10-30
 * Time: 19:16
 */
class ListNode {
    public int val;
    public ListNode next;//ListNode储存的是结点类型

    public ListNode (int val) {
        this.val = val;
    }

}
public class MyLinkedList {
    public ListNode head;//链表的头引用

    public void creatList() {
        ListNode listNode1 = new ListNode(12);
        ListNode listNode2 = new ListNode(23);
        ListNode listNode3 = new ListNode(34);
        ListNode listNode4 = new ListNode(45);
        ListNode listNode5 = new ListNode(56);
        listNode1.next = listNode2;
        listNode2.next = listNode3;
        listNode3.next = listNode4;
        listNode4.next = listNode5;
        this.head = listNode1;
    }
    //打印链表中的所有元素
    public void display() {
        ListNode cur = this.head;
        while(cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key) {
        ListNode cur = this.head;
        while(cur != null) {
            if(cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //得到单链表的长度
    public int size(){
        ListNode cur = this.head;
        int count = 0;
        while(cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }
    //头插法
    public void addFirst(int data) {
        ListNode node = new ListNode(data);
        node.next = this.head;
        this.head = node;
        /*if(this.head == null) {
            this.head = node;
        } else {
            node.next = this.head;
            this.head = node;
        }*/
    }
    //尾插法
    public void addLast(int data) {
        ListNode node = new ListNode(data);
        if (this.head == null) {
            this.head = node;
        } else {
            ListNode cur = this.head;
            while (this.head != null) {
                cur = cur.next;
            }
            cur.next = node;
        }
    }

    /**
     * 找到index - 1位置的节点的地址
     * @param index
     * @return
     */
    public ListNode findIndex(int index) {
        ListNode cur = this.head;
        while (index != 0) {
            cur = cur.next;
            index--;
        }
        return cur;
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data) {
        if(index < 0 || index > size()) {
            System.out.println("index 位置不合法！");
            return;
        }
        if(index == 0) {
            addFirst(data);
            return;
        }
        if(index == size()) {
            addLast(data);
            return;
        }
        ListNode cur = findIndex(index);
        ListNode node = new ListNode(data);
        node.next = cur.next;
        cur.next = node;
    }

    /**
     * 找到 要删除的关键字key的节点
     * @param key
     * @return
     */
    public ListNode searchPerv(int key) {
        ListNode cur = this.head;
        while(cur.next != null) {
            if(cur.next.val == key) {
                return cur;
            }
            cur = cur.next;
        }
        return null;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key) {
        if(this.head == null) {
            System.out.println("单链表为空");
            return;
        }
        if(this.head.val == key) {
            this.head = this.head.next;
            return;
        }
        ListNode cur = searchPerv(key);
        if(cur == null) {
            System.out.println("没有你要删除的节点");
            return;
        }
        ListNode del = cur.next;
        cur.next = del.next;
    }
    //删除所有值为key的节点
    public ListNode removeAllKey(int key) {
        if(this.head == null) {
            return null;
        }
        ListNode prev = this.head;
        ListNode cur = this.head.next;

        while(cur != null) {
            if(cur.val == key) {
                prev.next = cur.next;
                cur = cur.next;
            } else {
                prev = cur;
                cur = cur.next;
            }
        }
        //最后处理头
        if(this.head.val == key) {
            this.head = this.head.next;
        }
        return this.head;
    }
    //清除链表中所有元素
    public void clear() {
        //this.head == null;
        while(this.head != null) {
            ListNode curNext = head.next;
            this.head.next = null;
            this.head = curNext;
        }
    }
}
